About

Snares Islands Flora: an introduction

The vascular flora of the Snares Islands is limited, at only 22 species (including one hybrid Poa). Despite this, my first impression of the main island was an island covered with lush vegetation. And there are still some botanical challenges – we failed to locate the fern Histiopteris incisa for instance. Vegetation communities on the Snares consist of five main types: forest (c.50-60% cover), tussock grassland (c.25-30%), shrubland (c.10%), herbfields (c.<1%) and herbaceous/turf seepage communities (c.1%).

Snares Island forest comprises two species of tree daisy: Olearia lyallii and Brachyglottis stewartiae, the former being the dominant species on the islands. Both have a very southern distribution between the Snares in the south (with Olearia also found on the Auckland Islands) and the Solander Islands, Foveaux Straight in the north. Shrubland contains the white-flowered variation of Veronica elliptica which occurs on the coast and on the tops, mostly bordering Olearia forest and which quickly colonise areas of forest windthrow and dieback. Tussock grassland is dominated by Poa tennantiana (wide leaved) and Poa astonii.

A major feature of sub-antarctic plant communities is the megaherbs. This feature is limited to only two sites on the main island of the Snares. They contain the impressive Stilbocarpa robusta and Anisotome acutifolia. The latter species is the only vascular plant species currently recognised as endemic to the Snares Islands. One recently described entity of Cook’s scurvy grass, Lepidium limenophylax, is also associated with these herbfields but mainly grows along the western and northern cliff tops of North East Island. Due to the limited area that they occupy, these last two species are listed as threatened. However, the populations on North East Island appear to be stable and healthy.

There are two low-lying herbaceous plants on the Snares with a New Zealand distribution limited to the sub-antarctic islands: Callitriche antarctica (which thrives in coastal and inland seepage areas) and Stellaria decipiens (glabrous native chickweed). Other species include a cushion plant (Colobanthus muscoides), a succulent herb (Crassula moschata), a small rush (Isolepis cernua) and a sedge (Carex trifida).

Stellaria decipiens, one of two Snares plants, with a New Zealand distribution restricted to the sub-antarctic islands Image: Antony Kusabs, Te Papa

The islands have always been free of introduced mammals but two introduced species of plant have made it to the island. These are Stellaria media (hairy chickweed) and the grass, Poa annua. The Department of Conservation are controlling the invasive Stellaria media and we only saw scattered plants on Gull Point in Boat Harbour, North East Island.

One of two weeds on the Snares Islands: Stellaria media, Gull Point, Boat Harbour, North East Island. Image: Antony Kusabs, Te Papa

Please see my ‘Snares Islands Flora‘ project page on Nature Watch NZ which provides more images and more information on habitat and distribution.

One objective while visiting the Snares was to collect mosses, liverworts and lichens. An overview of these collections and initial findings can be found in the Snares Islands – bryophytes and lichens blog.

I was one of four Te Papa Science staff to complete a 15 day multidisciplinary field study on the Snares Islands/Tini Heke in December 2013. We wish to thank the Department of Conservation, Hokonui Rūnaka, Te Rūnanga o Awarua, Te Rūnanga o Ōraka-Aparima & Waihōpai Rūnaka, who made our fieldwork possible.

You’re welcome Alex. Yes, the South Promontory and South-West Coast populations look healthy. One vegetation plot on the South Prom (Quadrant 18) which was dominated by Anisotome in the 1980’s, only has c.10% cover now, but judging by the numbers of plants in the area surrounding the plot, this suggests spatial change in population rather than a population decline in that area. NB: Colin Miskelly remembers a single plant from near the sinkhole, North Promontory, which he couldn’t locate this time. Unfortunately I cannot report on the Broughton Island population, as we didn’t land there this trip.

Hi Mick. Glad you enjoyed it. I’ll try to get another post published next week. It was certainly the trip of a lifetime. It was great to be able to photograph every vascular plant on the Snares in flower. Callitriche antarctica was the most difficult to image.